Seat reclining apparatus

ABSTRACT

A seat reclining apparatus includes a base plate, a ratchet plate, a lock member supported on a surface of the base plate which faces the ratchet plate so that the lock member is movable between engaged and disengaged positions, a rotational cam positioned between the base plate and the ratchet plate and rotates relative thereto by an operation of an operating member, and a welding protrusion which protrudes from the outer side of the base plate and is engaged with a holding portion. The welding protrusion includes a welding portion which is positioned closer to an outer peripheral side of the base plate than the outer toothed portion of the lock member in the engaged position, and a weld is applied so as to extend over the welding portion and an outer edge of the holding portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a seat reclining apparatus foradjustment of the seatback angle of a reclining seat.

2. Description of Related Art

Japanese Unexamined Patent Publication No. 2012-51466 discloses a knownseat reclining apparatus which includes a base plate which is fixed to aseat cushion side frame, a ratchet plate (ratchet) which is fixed to aseatback side frame and provided on the inner periphery thereof with anannular internal gear, a rotational center shaft (hand-operated shaft)for the base plate and the ratchet plate, three lock members (pawls)which are supported on an inner side of the base plate (a surface of thebase plate which faces the ratchet plate) thereby to be movable(slidable) relative to the base plate in radial directions of therotational center shaft, a rotational cam which rotates with therotational center shaft, and a lock spring (spiral spring) which biasesand rotates the rotational center shaft.

An outer toothed portion is formed on an outer peripheral surface ofeach lock member. Each lock member is movable relative to the base plate(the associated guide groove) between an engaged position in which theouter toothed portion is engaged with the internal gear of the ratchetplate and a disengaged position in which the outer toothed portion isdisengaged radially inwards from the internal gear of the ratchet plate.

The rotational cam is rotatable between a locked position, to positioneach lock member in the engaged position, and an unlocked position, toposition each lock member in the disengaged position. The lock springbiases the rotational center shaft in a direction so as to rotate therotational cam toward the locked position.

Welding protrusions are projected from an outer side of the base plate(a surface of the base plate which faces the seat cushion side frame).The welding protrusions can be engaged in a holding portion which isformed in the seat cushion side frame as a through-hole (note thatneither the seat cushion frame nor the holding portion is disclosed inJapanese Unexamined Patent Publication No. 2012-51466). The weldingprotrusions are fixed to the seat cushion side frame by welding an outerperipheral edge of each welding protrusion to the seat cushion sideframe (an outer edge of the holding portion).

When an operating lever (hand-operated lever) which is linked with therotational center shaft is not manually rotated, the rotational camrotates toward the locked position by the rotational biasing force ofthe lock spring, which causes each lock member to move toward theengaged position. Accordingly, the outer toothed portion of each lockmember is engaged with the internal gear of the ratchet plate, so thatthe seatback side frame (seatback) becomes non-rotatable relative to theseat cushion side frame (seat cushion).

On the other hand, the operating lever is manually rotated against therotational biasing force of the lock spring, the rotational cam moves tothe unlocked position. Thereupon, each lock member having moved to theengaged position moves toward the disengaged position, which causes theouter toothed portion of each lock member to be disengaged from theinternal gear of the ratchet plate. As a result, the seatback side frame(seatback) becomes rotatable relative to the seat cushion side frame(seat cushion) (i.e., the angle of the seatback becomes adjustablerelative to the seat cushion).

The aforementioned welding protrusions of the seat reclining apparatusdisclosed in the above-mentioned Japanese Unexamined Patent PublicationNo. 2012-51466 are positioned closer to the center of the base plate(closer to the inner peripheral side of the base plate) than the outertoothed portion (the outer periphery) of each lock member in the engagedposition.

If welding is applied so as to extend over an outer peripheral edge ofeach welding protrusion and the seat cushion side frame (an outer edgeof the aforementioned holding portion of the seat cushion side frame),heat caused by welding reaches the inner side of the base plate throughthe inside of the base plate. Consequently, this heat eventually reachesthe lock member support portion on the inner side of the base platebecause the welding protrusions are positioned closer to the center ofthe base plate (closer to the inner peripheral side of the base plate)than the outer toothed portion (the outer periphery) of each lock memberin the engaged position.

Thereupon, the lock member support portion of the base plate (the innerside of the base plate) may be deformed (e.g., deformed to bulge towardthe lock member) by the aforementioned heat caused by welding, so thateach lock member may become incapable of sliding smoothly on the innerside (the lock member support portion) of the base plate.

SUMMARY OF THE INVENTION

The present invention provides a seat reclining apparatus which isstructured to reduce the possibility of movement of the lock member (s)relative to the base plate becoming unsmooth due to heat of weldingapplied between one or more welding protrusions and a holding portion(welding-protrusion holding portion) formed as a hole in either the seatcushion side frame or the seatback side frame even though the seatreclining apparatus is structured such that the welding protrusion (s)that is engaged in the holding portion protrudes from the outer side ofthe base plate that supports the lock member (s) by the inner sidethereof in a manner to allow the lock member (s) to move on the innerside thereof.

According to an aspect of the present invention, a seat recliningapparatus is provided, including a base plate, an outer side of whichfaces one of a seat cushion side frame and a seatback side frame; aratchet plate which includes an internal gear, the ratchet plate beingfixed to the other of the seat cushion side frame and the seatback sideframe so as to face the base plate while being rotatable relativethereto; a lock member supported on a surface of the base plate whichfaces the ratchet plate so that the lock member is movable between anengaged position in which an outer toothed portion formed on an outerperipheral surface of the lock member is engaged with the internal gearof the ratchet plate and a disengaged position in which the outertoothed portion is disengaged from the internal gear of the ratchetplate toward an inner peripheral side; a rotational cam which ispositioned between the base plate and the ratchet plate and rotatesrelative to the base plate and the ratchet plate in association with anoperation of an operating member between a locked position to positionthe lock member in the engaged position and an unlocked position toposition the lock member in the disengaged position; and a weldingprotrusion which protrudes from the outer side of the base plate and isengaged with a holding portion, which is formed as one of a through-holeand a bottomed hole in the one of the seat cushion side frame and theseatback side frame. The welding protrusion includes a welding portionwhich is positioned closer to an outer peripheral side of the base platethan the outer toothed portion of the lock member in the engagedposition, and a weld is applied so as to extend over the welding portionand an outer edge of the holding portion.

In the seat reclining apparatus according to the present invention, thewelding protrusion, which protrudes from the outer side of the baseplate, is provided with the welding portion that is positioned closer tothe outer peripheral side of the base plate than the outer toothedportion of the lock member in the engaged position.

Therefore, even when welding is applied so as to extend over the weldingportion of the welding protrusion and an outer edge of the holdingportion, the possibility of heat caused by the welding reaching theinner side of the base plate (a surface of the base plate which supportsthe lock member) through the inside of the base plate is small.

Accordingly, the possibility of the lock member support surface of thebase plate being deformed (e.g., deformed to bulge toward the lockmember) by the aforementioned heat caused by welding to thereby make thelock member incapable of sliding smoothly on the inner side (the lockmember support portion) of the base plate is small.

It is desirable for the base plate to be a press-molded product, whereina protrusion-corresponding recess is formed in the surface of the baseplate, which faces the ratchet plate, at a position corresponding to aposition of the welding protrusion, and for the lock member and theprotrusion-corresponding recess to be positioned to face each other.

Accordingly, although there is a slight possibility of heat caused bythe weld that extends over the welding portion of the welding protrusionand an outer edge of the holding portion reaching theprotrusion-corresponding recess to thereby deform a surface of theprotrusion-corresponding recess, since the lock member that is supportedby the inner side of the base plate is spaced from the inner surface ofthe protrusion-corresponding recess, even if the surface of theprotrusion-corresponding recess is deformed, there is no possibility ofthis deformation making movement of the lock member on the base plateunsmooth.

It is desirable for the welding protrusion to include a pair of side endsurfaces which are flat and spaced from each other in a rotationaldirection of the ratchet plate relative to the base plate, and for theholding portion to include a pair of flat portions which face the pairof side end surfaces of the welding protrusion, respectively.

Accordingly, a large contact area in a circumferential direction betweenthe holding portion (formed in either the seat cushion side frame or theseatback side frame) and the welding protrusion (formed on the baseplate) can be secured. Therefore, even if a collision load occursbetween the pair of side end surfaces of the welding protrusion and thepair of flat portions of the holding portion due to, e.g., a vehiclewhich incorporates the seat reclining apparatus colliding with anothervehicle, a high resistance to this collision load can be expected.

The present disclosure relates to subject matter contained in JapanesePatent Application No 0.2012-204643 (filed on Sep. 18, 2012) which isexpressly incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be discussed below in detail with referenceto the accompanying drawings, in which:

FIG. 1 is a side elevational view of a vehicle seat to which anembodiment of a seat reclining apparatus according to the presentinvention has been applied;

FIG. 2 is an exploded perspective view of the seat reclining apparatus;

FIG. 3 is a left-side elevational view of the seat reclining apparatus;

FIG. 4 is a right-side elevational view of the seat reclining apparatus;

FIG. 5 is a rear elevational view of the seat reclining apparatus;

FIG. 6 is a right-side elevational view of the seat reclining apparatusin a locked state and a seat cushion side frame;

FIG. 7 is a left-side elevational view of the seat reclining apparatusin a locked state and a seat cushion side frame;

FIG. 8 is a cross sectional view taken along the line VIII-VIII shown inFIG. 6, viewed in the direction of the appended arrows;

FIG. 9 is a cross sectional view taken along the line IX-IX shown inFIG. 6, viewed in the direction of the appended arrows;

FIG. 10 is a cross sectional view taken along the line X-X shown in FIG.6, viewed in the direction of the appended arrows;

FIG. 11 is an enlarged view of a portion of the seat reclining apparatuswhich is designated by the Roman numeral XI shown in FIG. 6;

FIG. 12 is a cross sectional view taken along the line XII-XII shown inFIG. 7, viewed in the direction of the appended arrows;

FIG. 13 is an external side (right-side) elevational view of a baseplate shown in FIGS. 2 and others;

FIG. 14 is an enlarged side view of a portion of the base plate and alock spring shown in FIGS. 2 and others;

FIG. 15 is an enlarged side view of a spring cover shown in FIGS. 2 andothers;

FIG. 16 is a diagram of the spring cover, viewed in the direction of thearrow XVI shown in FIG. 15;

FIG. 17 is a cross sectional view taken along the line XVII-XVII shownin FIG. 15, viewed in the direction of the appended arrows;

FIG. 18 is a right-side elevational view of a rotational center shaftshown in FIGS. 2 and others;

FIG. 19 is a cross sectional view taken along the line XIX-XIX shown inFIG. 18, viewed in the direction of the appended arrows;

FIG. 20 is a left-side elevational view of a rotational cam (first cam)shown in FIGS. 2 and others;

FIG. 21 is a cross sectional view taken along the line XXI-XXI shown inFIG. 8, viewed in the direction of the appended arrows, from which theseat cushion side frame, a retaining ring, rotation-stop pins and anannular flange are removed for clarity;

FIG. 22 is a view similar to that of FIG. 21, showing the seat recliningapparatus in an unlocked state from which two lock members are furtherremoved for clarity;

FIG. 23 is a view similar to that of FIG. 21, showing the seat recliningapparatus in an unlocked-state holding state;

FIG. 24 is an enlarged view of a portion of the seat reclining apparatuswhich is designated by the Roman numeral XI shown in FIG. 22;

FIG. 25 is an enlarged view of a wedge shown in FIGS. 2 and others; and

FIG. 26 is a view similar to that of FIG. 24, illustrating a modifiedembodiment of the seat reclining apparatus

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be hereinafter discussedwith reference to FIGS. 1 through 25. Directions described in thefollowing description are defined based on the directions of arrowsshown in the drawings. In the following description, the term “innerperipheral side” refers to the center side of a base plate 27 of theseat reclining apparatus 25 and the term “outer peripheral side” refersto the radially opposite side of the base plate 27 from the center sidethereof.

A vehicle seat 10 shown in FIG. 1 is a right-side seat and is providedwith a seat cushion 11 which is supported by a vehicle interior floor ofa vehicle (e.g., an automobile) via a seat rail, and a seatback 12 whichis rotatable relative to (pivoted at) the rear of the seat cushion 11. Apair of left and right seat cushion frames, made of metal, are installedinside the seat cushion 11 in a fixed state. Each seat cushion frame isa plate-shaped member extending in the forward/rearward direction(horizontal direction with respect to FIG. 1), and the rear end of eachseat cushion frame includes a rear frame (seat cushion side frame) 13(see FIG. 2, etc.), made of metal, which projects upward. The rear frame13 is provided with a seat-cushion-side connecting hole 14 formed as acircular through-hole with three engaging holes 15 formed at intervalsof 120 degrees (i.e. at equi-angular intervals) at the circumferencethereof. The three engaging holes 15 are formed in such a manner to berecessed radially outwards from the circumference of theseat-cushion-side connecting hole 14. Each engaging hole 15 issubstantially rectangular in shape, and both ends of each engaging hole15 in the lengthwise direction thereof (circumferential direction aboutthe center of the seat-cushion-side connecting hole 14) are formed bytwo flat portions 15 a which are parallel to each other. The vehicleseat 10 is provided inside the seatback 12 with a pair of left and rightseatback side frames 16 (only a lower part of the right seatback sideframe 16 is shown by two-dot chain lines in FIG. 2) made of metal whichare installed in a fixed state (see FIG. 2). Each seatback side frame 16is a plate-shaped member extending in the lengthwise direction of theseatback 12. Each seatback side frame 16 is provided, in a lower portionthereof (which becomes a rear portion thereof when the seatback 12 istilted forward), with a seatback-side connecting hole 17 formed as athrough-hole which includes a substantially square-shaped hole and atotal of four fitting holes 18 which are respectively formed on the foursides of the aforementioned square-shaped hole. Each fitting hole 18 issubstantially rectangular in shape.

The left and right rear frames 13 are installed in the internal space ofthe seatback 12. The left and right seatback side frames 16 arepositioned in between the left and right rear frames 13. The leftseatback side frame 16 and the left rear frames 13 face each other inthe leftward/rightward direction (vehicle widthwise direction) and theright seatback side frame 16 and the right rear frames 13 face eachother in the leftward/rightward direction (vehicle widthwise direction).The left rear frame 13 and the left seatback side frame 16 are connectedto each other to be rotatable via a rotational connecting shaft (notshown). On the other hand, the right rear frame 13 and the rightseatback side frame 16 are connected to each other via a seat recliningapparatus 25 to be rotatable about an axis extending in theleftward/rightward direction.

The seatback 12 (the seatback side frames 16) is rotatable about theaforementioned rotational connecting shaft and the seat recliningapparatus 25 relative to the seat cushion 11 (the rear frames 13).Specifically, the seatback 12 (the seatback side frames 16) is rotatablebetween a forwardly-tilted position shown by a two-dot chain linedesignated by 12A in FIG. 1 and a rearward-tilted position shown by asolid line designated by 12B in FIG. 1.

The detailed structure of the seat reclining apparatus 25 will bediscussed hereinafter.

The seat reclining apparatus 25 is provided with the base plate 27, twolock members (pawls) 36, a lock member (pawl) 37, a wedge (second cam)41, a rotational cam 47, a rotational center shaft 51, a ratchet plate57, a retaining ring 64, a lock spring 68 and a spring cover 72, whichare major elements of the seat reclining apparatus 25.

The base plate 27 is a metal disk member which is formed by pressmolding. The base plate 27 is provided on the outer edge of the leftside thereof with a projecting large-diameter annular flange 28. Thebase plate 27 is provided with an accommodation space radially inside ofthe large-diameter annular flange 28. The base plate 27 is provided at acenter thereof with a bearing hole 29 formed as a through-hole which iscircular in cross sectional shape. The base plate 27 is provided on theleft side thereof with three groove-forming projections 30 (see FIGS. 21through 24) which project and are arranged at intervals of 120 degreesabout the bearing hole 29. Each groove-forming projection 30 issubstantially in the shape of a sector. The three groove-formingprojections 30 are formed by pressing the right side of the base plate27 leftward using a mold when the base plate 27 is formed by pressmolding. As shown in the drawings, a circular-arc-shaped clearance isformed between the outer periphery of each groove-forming projection 30and the large-diameter annular flange 28. Both side surfaces of eachgroove-forming projection 30 (with respect to the circumferentialdirection of the base plate 27) are formed as flat guide surfaces 30 a,and the flat guide surfaces 30 a (opposed surfaces) of any two adjacentgroove-forming projections 30 (which face each other in thecircumferential direction) are parallel to each other, and a guidegroove 31 is formed therebetween. The base plate 27 is further provided,on the right side thereof on the opposite sides from the three guidegrooves 31, with a total of three welding protrusions 33 (see FIGS. 2,4, 6, etc.), respectively, which project rightward. The three weldingprotrusions 33 are formed by pressing the bottoms (left side surfaces)of the three guide grooves 31 rightward by a mold when the base plate 27is formed by press molding. The base plate 27 is further provided at thebases of the three guide grooves 31 with three protrusion-correspondingrecesses 32 which are formed by the mold (which presses left sidesurfaces the bases of the three guide grooves 31) on the opposite sidesfrom the three welding protrusions 33, respectively (see FIGS. 8, 9, 10,12 and 13). Each welding protrusion 33 is substantially rectangular inshape, and both end surfaces of each welding protrusion 33 in thelengthwise direction thereof are formed as side end surfaces 33 a whichare flat surfaces parallel to each other. In addition, a retainingprojection 34 is formed on a center portion of the inner periphery ofeach welding protrusion 33 to project slightly toward the center of thebase plate 27 (toward the inner peripheral side). The base plate 27 isfurther provided, on the right side thereof in the vicinity of the frontwelding protrusion 33 (the right welding protrusion 33 with respect toFIG. 13), with a pair of lock projections 35 which project rightward(see FIGS. 2, 13 and 14).

The two lock members 36 are installed in two of the three guide grooves31, specifically in the front guide groove 31 (the left guide groove 31with respect to FIG. 21) and the rear guide groove 31 (the right guidegroove 31 with respect to FIG. 21), and the lock member 37 and the wedge41 are installed in the upper guide groove 31 (the upper guide groove 31with respect to FIG. 21).

The two lock members 36 and the lock member 37 are press-molded productsmade of metal plates, and the thicknesses of the three lock members 36and 37 are substantially the same as the depths of the three guidegrooves 31. A cam groove 38 is formed in each of the three lock members36 and 37, while a wedge-engaging groove 39 is formed only in the lockmember 37. As shown in FIG. 24, the wedge-engaging groove 39 is providedwith a circumferential parallel portion 39 b, which extendssubstantially parallel to the circumferential direction about the axisof the base plate 27, and a pressed portion (pressure-receivingportion/abutment portion) 39 a, which extends obliquely toward the innerperipheral side from one end (the right end with respect to FIG. 24) ofthe circumferential parallel portion 39 b. The pressed portion 39 a isnot linear (flat) in shape, but rather is a curved surface which isconvex toward the space formed by the wedge-engaging groove 39 (towardthe wedge 41; toward the left down side with respect to FIG. 24)(however, the curvature of the pressed portion 39 a is extremely small,so that the pressed portion 39 a appears to be substantially straight tothe naked eye). The two lock members 36 and the lock member 37 are eachprovided on the circular-arc-shaped outer peripheral surface thereofwith an outer toothed portion 40. In addition, the right side surfacesof each lock member 36 and 37 are flat surfaces. Additionally, each lockmember 36 and 37 is provided on the left side thereof with an engagingprojection 40 a which projects leftward and has a substantiallyrectangular cross sectional shape.

The wedge 41, which can be installed in the space formed by thewedge-engaging groove 39 of the wedge-engaging groove of the lock member37, is a press-molded product made of a metal plate. The wedge 41 hassmaller outside dimensions than the two lock members 36 and the lockmember 37 and has substantially the same thickness as that of the twolock members 36 and the lock member 37.

The wedge 41 is symmetrical in shape with respect to a straight line L1as shown in FIG. 25, and both the left and right sides of the wedge 41lie flat on parallel planes. The wedge 41 is provided on the peripherythereof with an engaging portion 43, a pressing portion 44 and aslide-contact flat surface (surface contact portion) 45. The straightline L1 passes between the pressing portion 44 and the slide-contactflat surface 45. The peripheral surface of the engaging portion 43 is acircular arc surface which corresponds to a portion of an imaginarycylindrical surface 42 (the straight line L1 passing through the centralaxis thereof) positioned inside the wedge 41. The aforementionedcurvature of the pressed portion 39 a of the lock member 37 is smallerthan the curvature of the engaging portion 43 of the wedge 41. Thepressing portion 44 and the slide-contact flat surface 45 of the wedge41, which are formed to be symmetrical with respect to the straight lineL1, are positioned outside the imaginary cylindrical surface 42 and areeach formed from a flat surface inclined to the straight line L1. Thewedge 41 is further provided with a clearance-forming portion 46 whichis positioned on the engaging portion 43 side (the lower side withrespect to FIG. 25) of a straight line L2 which is orthogonal to thestraight line L1 and passes through the axis of the imaginarycylindrical surface 42. The clearance-forming portion 46 is formed of aportion of the wedge 41 which is positioned on the engaging portion 43side of a straight line L2 and positioned outside the imaginarycylindrical surface 42 (specifically on the right-hand side of theimaginary cylindrical surface 42 with respect to FIG. 25). A concavesurface 46 a (concave toward the inside of the wedge 41) which iscontinuous with the engaging portion 43 is formed on a peripheralsurface of the clearance-forming portion 46.

The lock members 36, the lock member 37 and the wedge 41 are provided inthe respective guide grooves 31 as shown in FIGS. 21 through 23. Theright side surfaces of the lock members 36, the lock member 37 and thewedge 41 are all in surface contact with base (flat) surfaces (left sidesurfaces) of the guide grooves 31, respectively.

The rotational cam 47 is a press-molded product made of a metal plateand substantially identical in thickness to the three guide grooves 31.The rotational cam 47 is provided in the center thereof with anon-circular center hole 48, which is formed as a through-hole that isshaped as a circle with linearly cut-off opposite sides. The rotationalcam 47 is provided, on the outer periphery thereof at intervals of 120degrees, with three cam projections 49. As shown in the drawings, therotational cam 47 is installed in the center of the aforementionedaccommodation space of the base plate 27. As shown in FIG. 20, etc., therotational cam 47 is provided, on the left side thereof at equi-angularintervals in the circumferential direction, with three rotationretaining projections 47 a which project leftward. The three rotationretaining projections 47 a are columnar in shape and mutually identicalin specification. As shown in FIGS. 20 and 24, the rotational cam 47 isprovided on the outer peripheries of the three cam projections 49 withthree curved pressing surfaces 50, respectively, which are convex towardthe outer peripheral side. The rotational cam 47 is further provided, onthe outer periphery thereof at equi-angular intervals at differentpositions from the three curved pressing surfaces 50, with threelock-member pressing portions 47 b.

The rotational center shaft 51 is made of metal and provided with a camconnecting shaft 52 and an annular flange 54.

The cam connecting shaft 52 is a tubular member having a non-circularcross section. Both ends of the cam connecting shaft 52 are open asclearly shown in FIG. 19. The cam connecting shaft 52 is geometricallysimilar in cross sectional shape to and slightly smaller in size thanthe non-circular center hole 48. The cam connecting shaft 52 is providedtherein with a connecting hole 53 which is also geometrically similar incross sectional shape to the non-circular center hole 48.

The annular flange 54 is integrally formed on the rotational centershaft 51 to project radially outwards from the left end of the camconnecting shaft 52. The annular flange 54 is in the shape of a flatplate orthogonal to the axis of the cam connecting shaft 52.

In addition, the annular flange 54 is provided at equi-angular intervalsin the circumferential direction thereof with a total of sixthrough-holes: a pair of small-diameter circular holes 55 a, a pair oflarge-diameter through-holes 55 b and a pair of elongated holes 55 c.The pair of small-diameter circular holes 55 a are circular holesidentical in diameter to the three rotation retaining projections 47 a.The pair of large-diameter through-holes 55 b are circular holesslightly greater in diameter than the pair of small-diameter circularholes 55 a (the rotation retaining projections 47 a). The pair ofelongated holes 55 c are elongated holes which are shaped such that theminor diameter of each elongated hole 55 c is identical to the diameterof each small-diameter circular hole 55 a (each retaining projection 47a) and that the major diameter of each elongated hole 55 c is greaterthan the diameter of each small-diameter circular hole 55 a (eachretaining projection 47 a).

The rotational center shaft 51 is fixed to the rotational cam 47 withthe two lock members 36, the lock member 37, the wedge 41 and therotational cam 47 arranged in a clearance between the annular flange 54and the base plate 27 and with the three rotation retaining projections47 a of the rotational cam 47 respectively engaged in one of the pair ofsmall-diameter circular holes 55 a, one of the pair of large-diameterthrough-holes 55 b and one of the pair of elongated holes 55 c. The camconnecting shaft 52 is loosely fitted into the non-circular center hole48 of the rotational cam 47, and the end (right end) of the camconnecting shaft 52 projects rightward from the right side of the baseplate 27 (see FIGS. 8 through 10). When the three rotation retainingprojections 47 a are engaged in one small-diameter circular hole 55 a,one large-diameter through-hole 55 b and one elongated hole 55 c,respectively, play between the three rotation retaining projections 47 aand the one small-diameter circular hole 55 a, the one large-diameterthrough-hole 55 b and the one elongated hole 55 c substantiallydisappears, so that the rotational cam 47 and the rotational centershaft 51 become integral with each other (in other words, the rotationalcam 47 and the rotational center shaft 51 are prevented from rotatingrelative to each other). Therefore, rotating the rotational center shaft51 on the axis thereof relative to the base plate 27 (to the bearinghole 29) causes the rotational cam 47 to rotate with the rotationalcenter shaft 51. In addition, since all the through-holes formed in theannular flange 54 are not formed as the small-diameter circular holes 55a but are formed in the above described manner, the three rotationretaining projections 47 a can be easily fitted into three holes (one ofthe pair of small-diameter circular holes 55 a, one of the pair oflarge-diameter through-holes 55 b and one of the pair of elongated holes55 c) formed in the annular flange 54.

The ratchet plate 57 is a press-molded metal product which is shapedinto a disk. The ratchet plate 57 is provided on the outer edge of theright side thereof with a small-diameter annular flange 58 having acircular shape, so that an accommodation space is formed radially insidethe small-diameter annular flange 58 on the right side of the ratchetplate 57. The ratchet plate 57 is provided at the center thereof with abearing hole 59 formed as a through-hole which is circular in crosssectional shape. The ratchet plate 57 is provided, on the left sidethereof at intervals of 90 degrees in the circumferential directionabout the bearing hole 59, with a total of four welding protrusions 60which project leftward. The ratchet plate 57 is provided on the outeredge of the left side thereof with an annular stepped portion 62 (seeFIGS. 8 through 10) that is positioned in the back of the small-diameterannular flange 58. In addition, the ratchet plate 57 is provided on aninner peripheral surface of the small-diameter annular flange 58 with aninternal gear 63. The ratchet plate 57 is further provided, atequi-angular intervals in the circumferential direction thereof on aninner peripheral surface of the small-diameter annular flange 58 whichis positioned one step to the left of the internal gear 63, with threeunlocked-state holding projections 57 a which project toward the innerperipheral side (see FIGS. 2 and 21 through 23). As shown in thedrawings, the inner periphery of each unlocked-state holding projection57 a is in the shape of a circular arc, the curvature center of whichcorresponds to the axis of the ratchet plate 57. The ratchet plate 57 isinstalled to cover the left side of the base plate 27 with thesmall-diameter annular flange 58 inserted into a clearance between theinner periphery of the large-diameter annular flange 28 and the outerperipheries of the three groove-forming projections 30. When the ratchetplate 57 is made to cover the base plate 27, the left side of theannular flange 54 faces the bottom (right side) of the aforementionedaccommodation space of the ratchet plate 57 with a clearance formedtherebetween, which prevents the rotational center shaft 51 from tiltingrelative to the axial direction thereof and prevents the two lockmembers 36, the lock member 37, the wedge 41 and the rotational cam 47from rattling in the aforementioned accommodation spaces of the baseplate 27 and the ratchet plate 57 in the axial direction of therotational center shaft 51.

The retaining ring 64 is an annular ring member made of metal. Theretaining ring 64 has a slightly greater outer diameter than that of thebase plate 27. The retaining ring 64 is provided at the left end thereofwith an annular adjacent portion 65 which projects toward the innerperipheral side (see FIGS. 8 through 10). The retaining ring 64 isfitted on the outer edges of the base plate 27 and the ratchet plate 57with the annular adjacent portion 65 positioned on (opposed to) the leftside of the annular stepped portion 62. The retaining ring 64 isprovided on the right end thereof with an annular swaging portion 66.The retaining ring 64 is fixed to the base plate 27 by swaging theannular swaging portion 66 against an annular recess formed on theperimeter of the right side of the base plate 27. Once the base plate 27and the retaining ring 64 are integrated (fixed to each other), theratchet plate 57 is positioned between the base plate 27 and theretaining ring 64 so that the ratchet plate 57 is rotatable relative tothe base plate 27 and the retaining ring 64 about the rotational centershaft 51 without coming off the base plate 27 or the retaining plate 64.

The lock spring 68 is a spiral spring that is formed by winding a metalbelt into a spiral and is installed on the right side of the base plate27. The end (inner end) of the lock spring 68 on the inner peripheralside is formed as a first locking portion 69 that is formed by bendingthe inner end of the lock spring 68 into a linear shape. The end (outerend) of the lock spring 68 on the outer peripheral side is formed as asecond locking portion 70 which extends in a direction substantiallyparallel to a radial direction of the lock spring 68.

The lock spring 68 is installed around the right end of the camconnecting shaft 52 that projects from the base plate 27. As shown inFIG. 14, the first locking portion 69 is locked onto a flat portion ofthe cam connecting shaft 52 which constitutes a portion of the outerperiphery of the cam connecting shaft 52, while the second lockingportion 70 is locked onto one of the locking projections 35.

When the lock spring 68 is installed onto the base plate 27 and therotational center shaft 51 (the cam connecting shaft 52) in the abovedescribed manner, the lock spring 68 is slightly resiliently deformed toproduce a biasing force that urges the rotational center shaft 51 torotate in one direction. This biasing force urges the rotational centershaft 51 to rotate counterclockwise with respect to FIGS. 21 through 23,and accordingly, the rotational cam 47 is in the locked position shownin FIG. 21 when no external force other than the biasing force of thelock spring 68 is exerted on the rotational center shaft 51. When therotational cam 47 is in the locked position, each lock-member pressingportion 47 b presses the associated lock member 36 or 37 in a lockingdirection (toward the outer peripheral side). In addition, the curvedpressing surface 50 of the specific cam projection 49 (specifically theupper cam projection 49 with respect to FIG. 21; the cam projection 49shown in FIG. 24) of the rotational cam 47 presses the engaging portion43 of the wedge 41 in a locking direction (toward the outer peripheralside), so that the wedge 41 slides toward the outer peripheral side ofthe base plate 27 while being guided by the flat guide surface 30 a withwhich the slide-contact flat surface 45 of the wedge 41 is in surfacecontact, and the pressing portion 44 of the wedge 41 partly contacts andpresses the pressed portion 39 a with a large force. Therefore, the lockmember 37 which is pressed both toward the flat guide surface 30 a(which is positioned on the right-hand side of the lock member 37 withrespect to FIG. 21) and in the locking direction moves to an engagedposition in which the outer toothed portion 40 of the lock member 37 isengaged with internal gear 63 of the ratchet plate 57, so that the lockmember 37 becomes immovable in the associated guide groove 31. On theother hand, each of the two lock members 36 is allowed to move in acircumferential direction within a gap defined between the associatedguide groove 31 and the associated lock member 36, each lock member 36comes into engagement with the internal gear 63 of the ratchet plate 57while moving (adjusting) in a circumferential direction within the gapdefined between the associated guide groove 31 and the associated lockmember 36. Accordingly, when the rotational cam 47 rotates to the lockedposition, each of the three lock members (the two lock members 36 andthe lock member 37) securely performs a locking operation, so that thebase plate 27 and the ratchet plate 57 are prevented from rotatingrelative to each other. In addition, the outer peripheral surfaces ofthe engaging projections 40 a of the three lock members 36 and 37 arepositioned closer to the outer peripheral side than the inner peripheralsurfaces of the three unlocked-state holding projections 57 a.

On the other hand, rotating the rotational center shaft 51 clockwisewith respect to FIGS. 21 through 23 against the rotational biasing forceof the lock spring 68 causes the rotational cam 47, which is in thelocked position, to rotate to the unlocked position shown in FIG. 22.Thereupon, each of the three lock-member pressing portions 47 b isdisengaged from the associated lock member 36 or 37 toward the innerperipheral side, thus causing the curved pressing surface 50 of thespecific cam projection 49 (specifically, the upper cam projection 49with respect to FIG. 21) of the rotational cam 47 to be disengaged inthe circumferential direction from the engaging portion 43 of the wedge41. Additionally, each cam projection 49 engages with the associated camgroove 38 to move the associated lock member 36 or 37 radially inwardsto the disengaged position shown in FIG. 22, which causes the outertoothed portions 40 of the three lock members 36 and 37 and the internalgear 63 of the ratchet plate 57 to be disengaged from each other tothereby allow the base plate 27 and the ratchet plate 57 to rotaterelative to each other. Additionally, the wedge 41 becomes freelymovable in the associated guide groove 31 within the area surrounded bythe associated flat guide surface 30 a, the lock member 37 (the pressedportion 39 a) and the rotational cam 47 (the associated cam projection49). Additionally, the outer peripheral surfaces of the engagingprojections 40 a of the three lock members 36 and 37 are positionedcloser to the inner peripheral side than the inner peripheral surfacesof the three unlocked-state holding projections 57 a.

The spring cover 72 is made of metal and is mounted to the right side ofthe base plate 27. The spring cover 72 is formed from a metal plate bypress molding. The base of the spring cover 72 includes a spring housingportion 73 which is non-circular in a side view and the entire left endsurface thereof is open. A circular through-hole 74 is formed in thecenter of the spring housing portion 73. The spring cover 72 is providedon the outer edge of the left end of the spring housing portion 73 withan engaging projection 75, which is V-shaped in cross section andprojects toward the outer peripheral side. In addition, the spring cover72 is provided, on the outer edge of the left end of the spring housingportion 73 at different circumferential positions from the engagingprojection 75, with two pressed lugs 76 which project toward the outerperipheral side. The two pressed lugs 76 are flat lugs which lie in aplane orthogonal to the leftward/rightward direction.

The spring cover 72 is installed onto the right side of the base plate27 with the end of the cam connecting shaft 52 positioned in thecircular through-hole 74 and with the spring housing portion 73positioned between the three welding protrusions 33. Fitting the springhousing portion 73 into the space between the three welding protrusions33 causes the retaining projections 34 of two of the three weldingprotrusions 33 to be engaged with two parts of the outer edge of thespring housing portion 73, respectively, and causes the retainingprojection 34 of the remaining one welding protrusion 33 to be engagedwith the end of the engaging projection 75. Accordingly, when the springcover 72 is installed onto the right side of the base plate 27, thespring cover 72 becomes integral with the right side of the base plate27.

As shown in FIG. 6, the base plate 27 of the seat reclining apparatus 25is installed onto the rear frame 13 with the three welding protrusions33 of the base plate 27 respectively engaged in the three engaging holes15 of the rear frame 13 and with the side end surfaces 33 a of eachwelding protrusion 33 respectively being in surface contact with thepair of flat portions 15 a of the associated engaging hole 15. The rearframe 13 and the base plate 27 are fixed to each other by applying aweld W1 (indicated by many small cross marks shown in FIG. 11 and hatchlines shown in FIG. 12), from the right side of the rear frame 13, toeach of three welding portions (only one of which is shown in FIG. 11)each of which extends over an outer peripheral edge (right edge withrespect to FIG. 11) of one engaging hole 15 and an outer peripheral edgeof the right end surface of the associated welding protrusion 33. Asshown in FIG. 11, the outer peripheral edge of the right end surface ofeach welding protrusion 33 (the position at which the weld W1 isapplied) is positioned closer to the outer peripheral side than theposition of the internal gear 63 (i.e., the positions of the outertoothed portions 40 of the three lock members 36 and 37 when each of thethree lock members 36 and 37 is in the engaged position) and the outerperipheral edges of the three protrusion-corresponding recesses 32 (seeFIGS. 11 and 13). In addition, when the base plate 27 is fixed to therear frame 13, an inner side surface of the rear frame 13 (the outeredge of the seat-cushion-side connecting hole 14) comes in contact withthe outer side surfaces of the two pressed lugs 76, which easily andsecurely prevents the spring cover 72 from coming off the right side ofthe base plate 27.

On the other hand, the ratchet plate 57 of the seat reclining apparatus25 is fixed to the seatback side frame 16 by respectively engaging thefour welding protrusions 60 in the four fitting holes 18 and applying aweld (not shown), from the left side of the seatback side frame 16, toan outer peripheral edge of each engaging hole 18 and an outerperipheral edge of the left end surface of the associated weldingprotrusion 60.

After the rear frame 13 and the seatback side frame 16 are connected tothe seat reclining apparatus 25, a connecting shaft (not shown) having anon-circular cross sectional shape which extends leftward from the baseend of an operating lever (operating member) 21 (see FIG. 1) ispress-fitted into the connecting hole 53 of the cam connecting shaft 52through the circular through-hole 74 of the spring cover 72 to be fixedto the rotational center shaft 51 (to the connecting hole 53).Therefore, rotating the operating lever 21 about the aforementionedconnecting shaft causes the rotational center shaft 51 to rotate withthe operating lever 21 (the aforementioned connecting shaft).

Operations of the vehicle seat 10 will be discussed hereinafter.

When no external force is applied to the operating lever 21, theoperating lever 21 is held in the non-operating position shown by asolid line in FIG. 1 by the rotational biasing force of the lock spring68. Additionally, when no external force is applied to the operatinglever 21, the rotational cam 47 is in the locked position and the lockmember 37 is in the engaged position, so that the seat recliningapparatus 25 is in a locked state. This prevents the seat cushion 11(the rear frame 13), which is integral with the base plate 27, and theseatback 12 (the pair of seatback side frames 16), which is integralwith the ratchet plate 57, from rotating relative to each other. On theother hand, rotating the operating lever 21 counterclockwise withrespect to FIG. 1 to the operating position shown by a two-dot chainline in FIG. 1 against the rotational biasing force of the lock spring68 causes the rotational cam 47 to rotate to the unlocked position, thuscausing each of the two lock members 36 and the lock member 37 to moveto the disengaged position, so that the seat reclining apparatus 25comes into an unlocked state. This allows the seat cushion 11 (the rearframe 13), which is integral with the base plate 27, and the seatback 12(the pair of seatback side frames 16), which is integral with theratchet plate 57, to rotate relative to each other.

When the seatback 12 (the pair of seatback side frames 16) is in afirst-stage locked position shown by a solid line in FIG. 1, rotatingthe operating lever 21 to the operating position to move the seatreclining apparatus 25 to the unlocked state causes the seatback 12 torotate (tilt) forward by the rotational biasing force of a rotationalbiasing spring (not shown) installed in the vehicle seat 10. Thereupon,since the ratchet plate 57 rotates counterclockwise with respect toFIGS. 21 through 23 relative to the base plate 27, the seat recliningapparatus 25 comes into an unlocked holding state (i.e., a state inwhich the seat reclining apparatus 25 is held in the unlocked state) inwhich the three engaging projections 40 a (the outer peripheral surfacethereof) that are positioned closer to the inner peripheral side thanthe inner peripheral surfaces of the three unlocked-state holdingprojections 57 a radially oppose (face) (to be in contact with) theinner peripheral surfaces of the three unlocked-state holdingprojections 57 a, respectively, as shown in FIG. 23 (which shows a stateof the interior of the seat reclining apparatus 25 when the seatback 12has slightly rotated forward from the first-stage locked position).Therefore, the operating lever 21 is prevented from moving toward thenon-operating position (the rotational cam 47 and the lock member 37 arealso prevented from moving toward the locked position and the engagedposition, respectively), so that the seatback 12 rotates to theaforementioned forwardly-tilted position (shown by a two-dot chain linedesignated by 12A in FIG. 1) by the rotational biasing force of theaforementioned rotational biasing spring. When the seatback 12 ispositioned in between a position (shown in FIG. 23) slightly rotatedforward from the first-stage locked position and the forward-tiltedposition (shown by a two-dot chain line designated by 12A in FIG. 1),the seat reclining apparatus 25 is held in the aforementioned unlockedholding state.

On the other hand, when the seatback 12 is positioned at or behind thefirst-stage locked position shown by a solid line in FIG. 1, if onerotates the operating lever 21 in the non-operating position to theoperating position while applying a rearward force to the seatback 12(e.g., by the back of an occupant sitting in the vehicle seat 10) tochange the seat reclining apparatus 25 to an unlocked state, theseatback 12 rotates rearward. Subsequently, if one returns the operatinglever 21 to the non-operating position upon tilting the seatback 12 to adesired rearward-tilted position, the rotational cam 47 moves back tothe locked position while each lock member 36 and 37 moves back to theengaged position by the rotational biasing force of the lock spring 68,so that the seatback 12 (the pair of seatback side frames 16) is held atthe desired tilted position.

The wedge 41 of the above described embodiment of the seat recliningapparatus 25 is provided with the slide-contact flat surface 45, whichcomes in surface contact with the adjacent flat guide surface 30 a ofthe associated groove-forming projection 30. Therefore, when the seatreclining apparatus 25 is in the locked state, even if forward orrearward loads are exerted on the seatback 12 to thereby cause theaforementioned adjacent flat guide surface 30 a and the slide-contactflat surface 45 to come into contact with each other with a large forcedue to, e.g., a vehicle which incorporates the seat reclining apparatus25 colliding with another vehicle, concentrated loads do not easilyoccur between the aforementioned adjacent flat guide surface 30 a (theassociated groove-forming projection 30) and the wedge 41.

In addition, since the pressed portion 39 a of the lock member 37 is acurved surface that is convex toward the wedge 41 though the pressingportion 44 of the wedge 41 is flat in shape, even if an error exitsbetween the shape of the wedge 41 (the pressing portion 44) and thedesign shape thereof, there is little possibility of the wedge 41becoming positionally unstable when the rotational cam 47 rotates, sothat the operation of the wedge 41 does not easily become unsmooth.

Additionally, since the press portion 39 a of the lock member 37 has aprofile that is close to that of the pressing portion 44 of the wedge 41(has a curved profile that is close to a flat surface), the wedge 41(the pressing portion 44) or the lock member 37 (the pressed portion 39)easily deforms plastically into the same shape as the pressed portion 39a of the lock member 37 or the pressing portion 44 of the wedge 41,respectively, when the pressing portion 44 of the wedge 41 and thepressed portion 39 a of the lock member 37 come into contact with eachother with a large force due to, e.g., a vehicle which incorporates theseat reclining apparatus 25 colliding with another vehicle. If one ofthe pressing portion 44 of the wedge 41 and the pressed portion 39 a ofthe lock member 37 becomes deformed into the same shape as the other,the contact state between the pressing portion 44 of the wedge 41 andthe pressed portion 39 a of the lock member 37 becomes a surface contactstate, which reduces the possibility of large concentrated loadsoccurring therebetween. Accordingly, one or both of the wedge 41 and thelock member 37 can be efficiently prevented from being deformed ordamaged.

In addition, the seat reclining apparatus 25 has only one wedge (thewedge 41) while having more than one lock member (the two lock members36 and the lock member 37). Therefore, when the outer toothed portion 40of the lock member 37 which is pressed in the locking direction by thewedge 41 is engaged with the internal gear 63 of the ratchet plate 57,the positions of the lock member 37 and the ratchet plate 57 are fixed(a positional reference is determined), and the lock member 37 becomesimmovable in the associated guide groove 31. On the other hand, each ofthe remaining two lock members 36 is allowed to move in acircumferential direction within the gap defined between the associatedguide groove 31 and the associated lock member 36, thus being engagedwith the internal gear 63 of the ratchet plate 57 while moving, asappropriate, in a circumferential direction within the gap definedbetween the associated guide groove 31 and the associated lock member36. Accordingly, since all the three lock members, i.e., the two lockmembers 36 and the lock member 37, operate with reliability when therotational cam 47 rotates, the seat reclining apparatus 25 can reliablyperform locking and unlocking operations.

Additionally, when the seat reclining apparatus 25 comes into the lockedstate, the wedge 41 comes into contact with the following three members:the rotational cam 47, the lock member 37 and the base plate 27 (theadjacent flat guide surface 30 a of the associated groove-formingprojection 30), so that the behavior of the wedge 41 is appropriatelycontrolled.

Additionally, the wedge 41 has the concave surface 46 a that forms aclearance between the wedge 41 and the associated curved pressingsurface 50 of the rotational cam 47 when facing the associated curvedpressing surface 50 of the rotational cam 47 as shown in FIG. 24. Theconcave surface 46 a is a concave surface which faces a protrusionconstituting the associated curved pressing surface 50 and has a shapecapable of approaching the associated curved pressing surface 50, andaccordingly, the clearance between the associated curved pressingsurface 50 of the rotational cam 47 and the concave surface 46 a whenthe rotational cam 47 is in the unlocked position is narrow.

If an occupant pushes the seatback 12 rearward or forward when the seatreclining apparatus 25 is in the locked state, a force in thecircumferential direction of the base plate 27 is exerted on the outertoothed portion 40 of each of the two lock members 36 and the lockmember 37 from the internal gear 63 of the ratchet plate 57, and acomponent of this force which is directed toward the inner peripheralside becomes a force urging the two lock members 36, the lock member 37and the wedge 41 toward the inner peripheral side (toward the rotationalcam 47 side).

In this state, upon an occupant unlocking the seat reclining apparatus25, the curved pressing surface 50 of the rotational cam 47 moves awayfrom the wedge 41 in the circumferential direction of the rotational cam47 (the base plate 27). Thereupon, the wedge 41 which receives theaforementioned component of force (which is directed toward the innerperipheral side) moves toward the rotational cam 47. However, since theclearance between the concave surface 46 a of the wedge 41 and theassociated curved pressing surface 50 of the rotational cam 47 is narrow(the distance therebetween is small) as mentioned above, a highcollision speed of the wedge 41 against the rotational cam 47 does noteasily occur even if the concave surface 46 a of the wedge 41 collideswith the associated curved pressing surface 50 of the rotational cam 47,so that the possibility of a loud sound (noise) of such a collisionbeing produced between the wedge 41 (the concave surface 46 a) and therotational cam 47 (the associated curved pressing surface 50) is small.

Additionally, the pair of small-diameter circular holes 55 a, the pairof large-diameter through-holes 55 b and the pair of elongated holes 55c are formed in the annular flange 54 that rotates with the rotationalcenter shaft 51, and the three rotation retaining projections 47 a areprojected from the rotational cam 47 to be engaged in one of the pair ofsmall-diameter circular holes 55 a, one of the pair of large-diameterthrough-holes 55 b and one of the pair of elongated holes 55 c,respectively. Therefore, when the rotational center shaft 51 rotates,this rotational operating force is transmitted to the three rotationretaining projections 47 a via the one of the pair of small-diametercircular holes 55 a, the one of the pair of large-diameter through-holes55 b and the one of the pair of elongated holes 55 c that are formed inthe annular flange 54. The magnitude of the force transmitted from therotational center shaft 51 (the annular flange 54) to the rotational cam47 is equal to the magnitude of the rotation moment (torque) of therotational center shaft 51 (the annular flange 54) divided by the directdistance (distance in a radial direction of the annular flange 54) fromthe axis of the rotational center shaft 51 to the one of the pair ofsmall-diameter circular holes 55 a, the one of the pair oflarge-diameter through-holes 55 b or the one of the pair of elongatedholes 55 c. Since the pair of small-diameter circular holes 55 a, thepair of large-diameter through-holes 55 b and the pair of elongatedholes 55 c, which are formed in the annular flange 54, are positionedcloser to the outer peripheral side than the cam connecting shaft 52(the non-circular center hole 48 of the rotational cam 47), theaforementioned direct distance is longer than the radius of the camconnecting shaft 52 (the radius of the non-circular center hole 48 ofthe rotational cam 47). Therefore, the force transmitted from therotational center shaft 51 (the annular flange 54) to the rotational cam47 does not become too large. Accordingly, even if a force urging theoperating lever 21 to rotate beyond a predetermined normal range ofrotation is produced (even if a force urging the operating lever 21 torotate in the direction reverse to the operating position beyond thenon-operating position or in the direction reverse to the non-operatingposition beyond the operating position is produced) as a result of,e.g., a foot of an occupant accidentally coming into contact with theoperating lever 21, the possibility of the rotational cam 47 or therotational center shaft 51 (the annular flange 54) being deformed issmall.

Additionally, the three welding portions (to each of which the weld W1has been applied), which are formed on outer peripheral portions of thethree welding protrusions 33 that are projected from the base plate 27,are positioned closer to the outer peripheral side than the outertoothed portions 40 of the three lock members 36 and 37 which arepositioned in the engaged position. Therefore, the possibility of heatof the weld W1 reaching and deforming a portion of the bottom of each ofthe three guide groove 31 on which the associated lock member 36 or 37slides (e.g., deforming this portion so that it protrudes toward theassociated lock member 36 or 37) is small. Additionally, even if heat ofthe weld W1 reaching each of the three protrusion-corresponding recesses32, which are respectively positioned directly behind the three weldingprotrusions 33, and the inner surfaces of the threeprotrusion-corresponding recesses 32 are deformed by this heat, thisdeformation has no effect on the operation of each lock member 36 and 37because the inner surfaces of the three protrusion-correspondingrecesses 32 are spaced from the three lock members 36 and 37.Accordingly, the possibility of each lock member 36 and 37 becomingincapable of sliding on an inner side surface (the associated guidegroove 31) of the base plate 27 due to heat of the weld W1 is small.

Additionally, since the pair of side end surfaces 33 a of each weldingprotrusion 33 are in surface contact with the pair of flat portions 15 aof the associated engaging hole 15, it is possible to secure a largecontact area between each welding protrusion 33 (the pair of side endsurfaces 33 a) and the associated engaging hole 15 (the pair of flatportions 15 a). Accordingly, even if a collision load occurs between thepair of side end surfaces 33 a of each welding protrusion 33 and thepair of flat portions 15 a of the associated engaging hole 15 due to,e.g., a vehicle which incorporates the seat reclining apparatus 25colliding with another vehicle, the seat reclining apparatus 25 canexhibit high resistance to this collision load.

Although the present invention has been described based on the aboveillustrated embodiment of the seat reclining apparatus, the presentinvention is not limited solely to this particular embodiment; variousmodifications to the above illustrated embodiment of the seat recliningapparatus are possible.

For instance, it is possible to fix the base plate 27 to the pair ofseatback side frames 16 and fix the ratchet plate 57 to the rear frame13.

In addition, the left rear frame 13 (the left seat cushion frame) andthe left seatback side frame 16 can be connected to each other via theseat reclining apparatus 25 instead of the right rear frame 13 (theright seat cushion frame) and the right seatback side frame 16 beingconnected to each other via the seat reclining apparatus 25.Additionally, it is possible to connect the left and right rear frames13 and the left and right seatback side frames 16 to each other via leftand right seat reclining apparatuses 25, respectively, and connect therotational center shafts 51 of the left and right seat recliningapparatuses 25 to each other via a connecting pipe, or the like, so thatthe left and right seat reclining apparatuses 25 move in synchronizationwith each other.

Since the wedge 41 is symmetrical in shape with respect to the straightline L1 as shown in FIG. 25, the wedge 41 can also be applied to theleft seat reclining apparatus 25 in the case where the seat recliningapparatus 25 is installed to each of the left and right sides of thevehicle seat 10 (or in the case where the seat reclining apparatus 25 isinstalled only onto the left side of the vehicle seat 10).

Additionally, it is possible to form the pressed portion 39 a of thelock member 37 into a linear (flat) shape and form the pressing portion44 of the wedge 41 into a curved surface (corresponding to the curvedsurface of the pressed portion 39 a in the above described embodiment,which is smaller in curvature than the engaging portion 43 of the wedge41) which is convex toward the pressed portion 39 a.

Additionally, as shown in FIG. 26, the lock member 37 and the wedge 41can be replaced by an integral-type lock member 37′, the shape of whichcorresponds to the shape of an integral combination of the lock member37 and the wedge 41 (note that a two-dot chain line shown in FIG. 26shows a contour line of a portion of the integral-type lock member 37′which corresponds to the wedge 41).

The seat reclining apparatus according to the present invention can beprovided with a plurality of wedges, each of which corresponds to thewedge 41, and a plurality of lock members (each of which has thewedge-engaging groove 39) can be pressed by the plurality of wedges. Inthis case, the number of the plurality of wedges can be equal to or lessthan the number of the plurality of lock members.

In addition, the wedge 41 can be omitted.

Additionally, the curved pressing surface 50 of the rotational cam 47 isnot required to be a curved surface so long as it is formed into a shapethat is convex toward the concave surface 46 a of the wedge 41; on theother hand, the concave surface 46 a of the wedge 41 is also notrequired to be a curved surface so long as it is formed into a shapethat is concave toward the opposite side from the associated curvedpressing surface 50 of the rotational cam 47.

Additionally, it is possible for the rotational center shaft 51 to beprovided, on the annular flange 54 side thereof, with rotation retainingprojections corresponding to the rotation retaining projections 47 a andfor the rotational cam 47 to be provided with a small-diameter circularhole(s), a large-diameter through-hole(s) and an elongated hole(s)corresponding to the small-diameter circular hole(s) 55 a, thelarge-diameter through-hole(s) 55 b and the elongated hole(s) 55 c,respectively.

Additionally, the number of rotation retaining projections 47 a and thenumber of holes 55 a, 55 b and 55 c can each be one in either case whererotation retaining projections corresponding to the three rotationretaining projections 47 a and holes corresponding to the holes 55 a, 55b and holes 55 c are formed on the rotational cam 47 and the rotationalcenter shaft 51 or the rotational center shaft 51 and the rotational cam47, respectively.

Additionally, the three engaging holes 15 of the rear frame 13 can beformed as bottomed holes, the ends of which on the opposite side of therear frame 13 from the base plate 27 side are closed, rather than asthrough-holes.

Additionally, the three protrusion-corresponding recesses 32 can beomitted from the base plate 27 by, e.g., forming the base plate 27 byforging.

Additionally, a through-hole (as a substitution for the bearing hole 29)greater in diameter than the bearing hole 29 can be formed in the centerof the base plate 27 to install the lock spring 68 in this through-hole(within the plate thickness of the base plate 27).

Additionally, the lock spring 68 and the spring cover 72 can beinstalled onto the left side of the ratchet plate 57, or a through-hole(as a substitution for the bearing hole 59) greater in diameter than thebearing hole 59 can be formed in the center of the ratchet plate 57 toinstall the lock spring 68 (which is installed onto the left side of theratchet plate 57) in this through-hole (within the plate thickness ofthe ratchet plate 57). In this case, the inner side of the seatback sideframe 16 (the edge of the seatback-side connecting hole 17), that isshown by two-dot chain lines in FIG. 2, is made to contact the outerperipheries of the two pressed lugs 76.

The seat reclining apparatus 25 can be modified to be a so-calledswing-pawl type in which each lock member (pawl) is allowed to move notonly linearly in a radial direction of the base plate 27 relative to thebase plate 27 but also in a radial direction of the base plate 27 whileswinging relative to the base plate 27.

In this case, the circumferentially opposite surfaces of each lockmember 36 and 37 that respectively face the flat guide surfaces 30 a inthe associated guide groove 31 can be formed as flat surfaces, or theflat guide surfaces 30 a can be replaced by curved guide surfaces whilethe circumferentially opposite surfaces of each lock member thatrespectively face the aforementioned curved guide surfaces 30 a can beformed as curved surfaces (surface contact portions) which can be insurface contact with the aforementioned curved guide surfaces 30 a.

The seat reclining apparatus 25 can be modified into a so-called releasetype that incorporates a release plate which is linked with therotational cam 47 and the three lock members 36 and 37 instead ofomitting the three cam projections 49 from the rotational cam 47.

Additionally, the number of the welding protrusions 33 is not limited tothree.

Furthermore, the aforementioned connecting shaft (not shown) of theoperating lever 21 can be retained so as not to come off the connectinghole 53 by installing a push nut onto the end of the connecting shaftafter the connecting shaft is inserted into the connecting hole 53.

Obvious changes may be made in the specific embodiment of the presentinvention described herein, such modifications being within the spiritand scope of the invention claimed. It is indicated that all mattercontained herein is illustrative and does not limit the scope of thepresent invention.

What is claimed is:
 1. A seat reclining apparatus comprising: a baseplate, an outer side of which faces one of a seat cushion side frame anda seatback side frame; a ratchet plate which includes an internal gear,said ratchet plate being fixed to the other of said seat cushion sideframe and said seatback side frame so as to face said base plate whilebeing rotatable relative thereto; a lock member supported on a surfaceof said base plate which faces said ratchet plate so that said lockmember is movable between an engaged position in which an outer toothedportion formed on an outer peripheral surface of said lock member isengaged with said internal gear of said ratchet plate and a disengagedposition in which said outer toothed portion is disengaged from saidinternal gear of said ratchet plate toward an inner peripheral side; arotational cam which is positioned between said base plate and saidratchet plate and rotates relative to said base plate and said ratchetplate in association with an operation of an operating member between alocked position to position said lock member in said engaged positionand an unlocked position to position said lock member in said disengagedposition; and a welding protrusion which protrudes from said outer sideof said base plate and is engaged with a holding portion, which isformed as one of a through-hole and a bottomed hole in said one of saidseat cushion side frame and said seatback side frame, wherein saidwelding protrusion includes a welding portion which is positioned closerto an outer peripheral side of said base plate than said outer toothedportion of said lock member in said engaged position, and wherein a weldis applied so as to extend over said welding portion and an outer edgeof said holding portion.
 2. The seat reclining apparatus according toclaim 1, wherein said base plate is a press-molded product, wherein aprotrusion-corresponding recess is formed in said surface of said baseplate, which faces said ratchet plate, at a position corresponding to aposition of said welding protrusion, and wherein said lock member andsaid protrusion-corresponding recess are positioned to face each other.3. The seat reclining apparatus according to claim 1, wherein saidwelding protrusion comprises a pair of side end surfaces which are flatand spaced from each other in a rotational direction of said ratchetplate relative to said base plate, and wherein said holding portionincludes a pair of flat portions which face said pair of side endsurfaces of said welding protrusion, respectively.